1. Technical Field
The present invention relates generally to location determination and more specifically to determining the location of a mobile electronic device.
2. Background Information
A variety of different types of mobile electronic devices (such as cellular telephones, personal digital assistants (PDAs), Personal Navigation Devices (PNDs), hand-held computers, a notebook computer, etc.) are capable of determining their approximate geographic locations. Typically, such devices turn to one of several location determination methods (LDMs). For example, some mobile electronic devices rely upon the global positioning system (GPS) to determine their location. Such devices typically include a GPS receiver, having an antenna tuned to frequencies transmitted by GPS satellites, and a highly-stable clock, that together permit location determination using a GPS algorithm. In some cases, the algorithm may implement Assisted GPS (A-GPS) where additional information provided from a remote assistance server is used to improve location accuracy. For example, an assistance server may interoperate with the device to compare fragmentary signals received at the device with complete signals received at the server. Similarly, the assistance server may provide orbital data for GPS satellites and/or information concerning ionospheric conditions to the device.
Other mobile electronic devices may forgo GPS, and instead determine their location based upon the known locations of cell sites of a cellular phone network. Such devices typically establish a wireless connection with one or more nearby cell sites. The location of the device is approximated based upon the location of the nearest cell site (for example the one with the strongest signal), determined by triangulation among the locations of several cell sites, or by another similar technique.
Other mobile electronic devices may determine their location based upon the known locations of network access points, for example Wireless Fidelity (Wi-Fi) access points, Worldwide Interoperability for Microwave Access (WiMAX) access points, or similar network access points. The location of the device is approximated based upon the location of the nearest access point, determined by triangulation among several access points, or determined by another technique.
Still other mobile electronic devices rely upon interaction with a user to determine their location. In such cases, the user may be prompted to report their approximate location by inputting a text-string, for example a street address; by selecting a point on a displayed map; or by some other interactive technique. In this manner, the device comes to know its approximate location.
The location determination capabilities of portable electronic devices has led to a proliferation of location-based services (LBS's). An LBS is a service that exploits knowledge of a device's location, and/or the location of other devices, to provide location-specific information, notifications, interactive capabilities, and/or other functionality. For example, an LBS may provide information regarding nearby services, such as identifying the nearest automatic teller machine (ATM); information regarding nearby businesses, such as identifying the nearest restaurant of a particular type; information concerning the local environment, such as providing a local weather report; or other types of location-specific information. Similarly, an LBS may provide proximity-based alerts, for example, a notification of an ongoing sale when a user is proximate a particular store, or a notification that a “buddy” is nearby. Further, an LBS may offer access to certain interactive applications, games, downloadable-content, and the like, when a user is proximate a particular location. A wide variety of other LBS's are also possible.
While some LBS's do not require highly-accurate location knowledge, the usefulness of other LBS's may be seriously impaired by inaccuracies. For example, an LBS that provides a local weather report may tolerate considerable location-error absent any adverse impact on the user experience. In contrast, an LBS designed to alert a user of an ongoing sale as they enter a store may function poorly if knowledge of the user's location is inaccurate by a few hundred feet. The alert may be inadvertently triggered when a user simply walks or drives down a street within a few blocks of the store, more likely annoying the user than enticing them to buy merchandise. Similarly, an LBS designed to identify the nearest ATM may misdirect a user if knowledge of a user's location is inaccurate. The user may become annoyed upon noticing a closer ATM, losing confidence in the LBS.
Further, many existing LDMs do not provide locations in the most specific or most convenient form. For instance, a user of a mobile electronic device may be located at a place called “Corner Coffee” at the address of “120 Main Street.” A conventional LDM may simply identify a geographic position, for example, latitude and longitude, for the user. The name of the place and address however are more descriptive and are often preferable. For example, if the user desires to share his or her location with others, the place name and street are clearly more intelligible to another human. Similarly, if targeted content is to be displayed to the user, the place name and street address is more specific than the geographic position, and thus content can be better directed.
While more advanced location-determination infrastructure and/or more advanced hardware in mobile electronic devices may be employed in attempts to improve location accuracy and address the other above discussed shortcomings, such approaches are often commercially impracticable. There are considerable sunk costs in existing location determination infrastructure, and improved systems are likely to only slowly emerge into widespread use. Similarly, there is a sizable base of existing mobile electronic devices. Despite their limitations, these devices are likely to be in service for some time into the future.
Accordingly, there is a need for a system and method to more accurately determine the location of a mobile electronic device, which is compatible with existing location determination infrastructure and mobile electronic device hardware.